PALEONTOLOGY:
Whiff of Gas Points to Impact Mass Extinction
Richard A. Kerr
On page 1530, geochemists report that they have detected the noble gases helium and argon apparently trapped in the molecular cages of carbon "buckyballs," or fullerenes, extracted from rock laid down at the Permian-Triassic extinction 251 million years ago. Analysis of these gases shows, the researchers say, that their isotopic compositions are much more like those found in meteorites than on Earth. Thus, they conclude that a giant impactor delivered the chemicals to Earth just when the extinctions occurred.